This invention relates generally to an apparatus, commonly referred to as an inflator, for use in inflating an inflatable device such as an inflatable vehicle occupant restraint of a respective inflatable restraint system. More specifically, the invention relates to an inflator device containing a fluid fuel material adapted to be burned to produce gaseous inflation products and which inflator device has an inflation output adaptive to selected operating conditions and parameters.
Various arrangements are known in the art whereby inflatable restraints, e.g., airbags, are used to protect an occupant of an automotive vehicle, in the event of a collision. In addition, various inflatable restraint system arrangements have been proposed wherein the inflation of an airbag is adjusted based on factors such as, for example, the speed of deceleration of the vehicle and seat belt usage by the occupant.
For example, U.S. Pat. No. 5,323,243 discloses an occupant sensing apparatus for use in an occupant restraint system. The disclosed sensing apparatus preferably monitors the passenger seat in the vehicle to detect the presence, position and weight of an object on the seat. A control algorithm is performed to control inflation of the airbag, responsive to the detected values.
U.S. Pat. No. 5,074,583 discloses an airbag system for an automobile including a seating condition sensor that detects a seating condition of a passenger with respect to seat position, reclining angle, as well as passenger size and posture. The invention seeks to operate the airbag system in accordance with the seating condition of the passenger such that the inflated bag is brought into optimal contact with the occupant.
In addition, many types of inflator devices have been disclosed in the art for the inflation of an airbag such as used in inflatable restraint systems. One such type of inflator device involves the utilization of a quantity of stored compressed gas which is selectively released to inflate an airbag. To properly inflate a typical airbag at an appropriate rate, this type of inflator device commonly requires the storage of a relatively large volume of gas at a relatively high pressure. As a result of the utilization of high storage pressures, the walls of the gas storage chamber of the inflator are typically relatively thick for increased strength. The combination of large storage volume and thick storage chamber walls results in a relatively heavy and bulky inflator design.
Another type of inflator device derives inflation gas from a combustible gas generating material which, upon ignition, generates a quantity of gas sufficient to inflate the airbag. Gas generating materials effective to produce inflation gas in the rates and quantities required in such applications may, however, produce various undesirable combustion products, including various solid particulate, e.g., residue, materials. The removal of such solid particulate materials, such as by the incorporation of a filtering device within or about the inflator, can undesirably increase the complexity of either or both inflator design and processing and can also increase the costs associated therewith.
In addition, the temperature of the gaseous emission of such inflator devices can typically vary between about 500.degree. F. (260.degree. C.) and 1200.degree. F. (649.degree. C.), dependent upon numerous interrelated factors including the desired level of inflator performance, as well as the type and amount of gas generant used therein, for example. Consequently, airbags used in conjunction with such inflator devices are typically constructed of or coated with a material resistant to such high temperatures. For example, in order for an airbag to resist or avoid suffering having a hole burned through the airbag fabric as a result of exposure to such high temperatures, it is common airbag construction to include a coating of neoprene or one or more neoprene coated patches can be placed at the locations of the airbag on which the hot gas will initially impinge. As will be appreciated, such specially fabricated or prepared airbags are typically more costly to manufacture and produce.
Further, while vehicular inflatable restraint systems are preferably designed to be properly operational over a broad range of conditions, the performance of inflator devices of such design can be particularly sensitive to changes in ambient conditions, especially changes in temperature. For example, operation at very low temperatures, such as temperatures of -40.degree. F. (-40.degree. C.), can affect the performance of various propellants, and thus undesirably lower airbag pressure resulting from an inflator which contains a fixed available amount of propellant.
A third type of inflator device forms airbag inflation gas from a combination of stored compressed gas and the combustion of a solid form of a pyrotechnic gas generating material. This type of inflator device is commonly referred to as a hybrid inflator. Hybrid inflators that have been proposed heretofore often have been subject to certain disadvantages. For example, inflator devices of such a design typically result in a gas having a relatively high particulate content.
Various specific inflator devices and assemblies have been proposed in the prior art. U.S. Pat. No. 5,263,740 discloses an assembly wherein within a single chamber is housed both an inflation gas and a first ignitable material, which is subsequently ignited therein.
The housing of both an inflation gas and an ignitable material within a single chamber can result in production and storage difficulties. For example, concentration gradients of such components, both initially and over time as the device awaits actuation, can increase the potential for the release therefrom of ignitable material into the airbag prior to complete ignition, as well as increasing the relative amount of incomplete products of combustion released into the associated airbag.
A new type an inflator, called a "fluid fueled inflator," has been developed. Such inflators are the subject of commonly assigned U.S. Pat. No. 5,470,104, Smith et al., issued Nov. 28, 1995; U.S. Pat. No. 5,494,312, Rink, issued Feb. 27, 1996; and U.S. Pat. No. 5,531,473, Rink et al., issued Jul. 2, 1996, the disclosures of which are fully incorporated herein by reference.
Such an inflator device utilizes a fuel material in the form of a fluid, e.g., in the form of a gas, liquid, finely divided solid, or one or more combinations thereof, in the formation of an inflation gas for an airbag. In one such inflator device, the fluid fuel material is burned to produce gas which contacts a quantity of stored pressurized gas to produce inflation gas for use in inflating a respective inflatable device.
While such inflators avoid or minimize at least some of the above-identified shortcomings of prior inflator devices, there remains a need for an inflator device of simple design and construction, which is effectively operable using a variety of fuels, oxidants, and stored gases, and which, as compared to known inflation devices, can better vary output parameters such as the quantity, supply, and rate of supply of inflation gas, dependent on selected operating conditions such as ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.